Microwave heating technology has not only been applied in conventional industries (e.g., for dehydration of wood or brewers' yeast, for vulcanization of rubber, for thawing meat, and so on) but also been applied in semiconductor industries, e.g., for annealing silicon wafers. Semiconductor manufactural process contains hundreds of processes and each of them poses impacts on the production capacity and the yield of the silicon wafers.
Here, the wafer annealing process is required to be performed after ion implantation. When three-valance or five-valance elements are implanted into a four-valance semiconductor, the issue of lattice defects is likely to arise, such that the properties of the semiconductor are drastically changed; hence, the anneal step should be performed to recover the lattice structure, remove lattice defects, and move impurity atoms from an interstitial site to a substitution site through anneal, so as to activate electrical properties. Due to the issues for continuous shrink of interface thickness and line width in semiconductor devices, some types of anneal, such as infrared anneal or far-ultraviolet laser anneal, have been facing the bottlenecks caused by the issues aforesaid; however, microwave annealing process is not subject to the aforementioned requirements.
However, the technical barrier of microwave anneal lies in the strict requirement for anneal uniformity, i.e., high yield. The microwave frequency adopted by the already commercialized microwave anneal equipment is usually using 5.8 GHz or higher rather than 2.45 GHz (the common industrial microwave frequency). Shrink in wavelength of commercialized microwave anneal equipment leads to suppression of standing-wave effects and thus achieves uniform annealed results. However, compared to the 2.45 GHz magnetron, the 5.8 GHz magnetron has higher costs but lower efficiency. Hence, a multi-mode microwave heating (annealing) device for microwave annealing process on silicon wafers or other to-be-heated objects is provided herein. The multi-mode microwave heating (annealing) device usually uses (but not subject to use) the common industrial heating frequency of 2.45 GHz, which is sufficient to increase the microwave heating efficiency and uniformity and further improves the production capacity as well as the yield of the to-be-heated objects.